1. Field of the Invention
The invention relates to a circuit for the measurement and recognition of an extremum output voltage of a frequency selective electronic measurement object, which is supplied with a fixed measurement frequency by a frequency generator and supplied with a tuning voltage, where the tuning voltage can be changed in steps for obtaining an optimum tuning voltage.
2. Brief Description of the Background of the Invention Including Prior Art
The type of circuit to which the invention relates is useful in the balancing of high frequency circuits in communication receivers. Upon the reaching of an optimum tuning the change in the tuning voltage can be interrupted and the tuning voltage can be maintained constant.
For example, German Patent Application Laid Open DE-OS No. 2,854,852 teaches an automatic balancing unit for such apparatus, where the high frequency circuits are tuned to the desired receiver frequency with three auxiliary oscillators and with analog storage elements coordinated to the auxiliary oscillators and with the employment of a phase locked loop. In this circuit, the tuner oscillator is also employed for the balancing. In addition, auxiliary oscillators are required corresponding to the number of the high frequency circuits to be tuned. The number of the required auxiliary oscillators and thus the material expenditures is increased in a particular way if for example during the tuning of a television receiver band I, band III and the bands IV and V are to be tuned. Here the danger exists of ambiguities between the frequencies of the tuner oscillator, of the auxiliary oscillators and of the received frequencies. It is disadvantageous for a practical realization of the reference tuning unit that the exciting windings of the auxiliary oscillators can generate undesired resonances and damping of the circuits with the individual coils in the high frequency circuits, which in addition can cause an uncontrolled detuning of the circuits, if the auxiliary oscillators are switched off after the tuning is performed.